FIG. 13 shows the first conventional example of a polar modulation transmitting apparatus. The polar modulation transmitting apparatus has a polar signal producing circuit 1201, an amplitude controlling circuit 1202, a phase-modulated signal producing circuit 1203, and a non-linear power amplifier 1204. In such a polar modulation transmitting apparatus, the polar signal producing circuit 1201 produces a signal corresponding to the amplitude and the phase of a transmitting modulated wave from an input signal, and the amplitude controlling circuit 1202 and the phase-modulated signal producing circuit 1203 produce an amplitude signal and a phase-modulated signal, respectively, based on this signal. While the non-linear power amplifier 1204 is operated in a non-linear saturation mode and has the phase modulated signal inputted thereto and amplitude modulates the phase modulated signal by changing a power source voltage according to the amplitude signal. In this manner, by operating the non-linear power amplifier 1204 in a non-linear saturation mode, current consumption can be reduced as compared to a case of using a linear power amplifier and hence the life span of a battery can be elongated in the transmitting apparatus driven by a battery (for example, see patent document 1).
FIG. 14 shows the second conventional example of a polar modulation transmitting apparatus. This polar modulation transmitting apparatus has a polar signal producing circuit 1301, a timing adjusting circuit 1302, an amplitude controlling circuit 1305, a phase-modulated signal producing circuit 1306, a power amplifier 1307, and in addition, an amplitude signal detecting circuit 1308, a phase signal detecting circuit 1309, and a PA calibration table 1310. By making a correction to the amplitude controlling circuit 1305 and the phase-modulated signal producing circuit 1306 by the use of this calibration table 1310, amplitude-amplitude distortion (AM-AM distortion) and amplitude-phase distortion (AM-PM distortion) of the power amplifier 1307 can be corrected. Moreover, by adjusting the timings of an amplitude signal and a phase signal by the timing adjusting circuit 1302, it is possible to correct a delay difference between paths of the amplitude signal and the phase signal and to prevent the deterioration of transmission quality caused by the delay difference (for example, see patent document 2). For example, according to W-CDMA standards, transmission quality is expressed by ACLR (Adjacent Channel Leakage power Ratio) and EVM (Error Vector Magnitude).
FIG. 15 shows the third conventional example of a polar modulation transmitting apparatus. In this polar modulation transmitting apparatus, delay circuits 1412, 1413 are added to the modulation section 1410. The timings of a drain voltage (amplitude) and a modulated wave signal (phase) are adjusted by the use of these delay circuits 1412, 1413 to correct a delay difference in path between the amplitude signal and the phase signal. With this, it is possible to prevent the deterioration of ACLR and EVM caused by the delay difference between the amplitude signal and the phase signal (for example, see patent document 3).
FIG. 16 shows the fourth conventional example of a polar modulation transmitting apparatus. This polar modulation transmitting apparatus has phase detecting means 1502, 1503 for detecting the phase of an RF output signal, amplitude detection means 1501 for detecting the envelope of the amplitude of the RF output signal, synchronization detecting means 1512 for detecting the synchronization between the phase and the amplitude of the RF output signal, and synchronization controlling means 1513 for controlling delay means 1515 on the basis of the detected synchronization. The timings of the amplitude signal and the phase signal are adjusted by the use of these means to correct the delay difference in path between the amplitude signal and the phase signal. With this, it is possible to prevent the deterioration of ACLR and EVM caused by the delay difference between the amplitude signal and the phase signal (for example, see patent document 4).
However, the first conventional example shown in FIG. 13 does not have timing adjusting means and hence can not correct the delay difference in path between the amplitude signal and the phase signal and hence can not prevent the deterioration of transmission quality caused by the delay difference.
Further, the polar modulation transmitting apparatuses of the second conventional example shown in FIG. 14 and the third conventional example shown in FIG. 15 do not have a synchronization circuit for synchronizing the amplitude signal and the phase signal automatically and hence do not have a method except for adjusting synchronization manually. Moreover, it is difficult for a common user to adjust synchronization when the user uses a product after the product is shipped.
Still further, the polar modulation transmitting apparatuses of the fourth conventional example shown in FIG. 16 is configured to detect an amplitude envelope and a phase from the RF output signal of a multiplier or a power amplifier. However, to detect the synchronization between the amplitude signal and the phase signal by such a configuration, a signal in an RF band needs to be demodulated into a base band by some means, which results in using a circuit having a delay that is too large to neglect such as low pass filter. As a result, this may vary delay at the time of detection and reduce the accuracy of detection of delay.    [Patent document 1] Specification of U.S. Pat. No. 6,377,784B2    [Patent document 2] Specification of U.S. Pat. No. 6,366,177B1    [Patent document 3] Japanese Examined Patent Publication No. 6-54877 (FIG. 6)    [Patent document 4] Japanese Patent Publication No. 2002-530992 (FIG. 2)